Method of and apparatus for cleaning by ultrasonic waves



April 26, 1949. FRUTH 2,468,550

METHOD OF AND APPARATUS FOR CLEANING BY ULTRASONIC WAVES. Flled Oct 271944 2 Sheets-Sheet l [War H. F. F RUTH METHOD OF AND APPARATUS FORCLEANING BY ULTRASONIC WAVES April 26, 1949.

Filed Oct. 27, 1944 2 Sheets-Sheet 2 Patented Apr. 26, 1949 METHOD OFAND APPARATUS FOR CLEAN- ING BY ULTRASONIC WAVES Hal F. Fruth, Chicago,Ill., assignor to Motorola, Inc., a corporation of Illinois ApplicationOctober 27, 1944, Serial No. 560,685

4 Claims. 1

This invention relates to a method of and apparatus for cleaning textilefabric articles by ultra-sonic waves and, while it is of generalapplication, it is particularly suitable for embodiment in domesticwashing machines.

Heretofore there have been proposed numerous domestic washing machines,all of which operated on the principle of agitating or tumbling thearticles to be cleaned in a washing emulsion or other cleaning fluid.However, it has been found that, if the agitation is made suflicientlyintense to approximate hand washing or scrubbing on a washboard, thearticles being cleaned are severely strained, abraded and otherwisedamaged. These eflects are of course due to th harsh action of theirregular surface of the agitator or impeller of the machine operatingat relatively high speed against the articles, which offer increasedresistance to agitation due to the fact that they are saturated with thecleaning fluid. According to the present invention, this harsh action ofa mechanical agitator or impeller is replaced by a rapid and intenseagitation and circulation of the washing emulsion through the articlesby developing therein ultra-sonic waves.

It is an object of the invention, therefore, to provide a new method of,and apparatus for, cleaning textile fabric articles by means of which athorough cleaning is effected without resortin to intense agitation bymechanical agitators or impellers.

It is another object of the invention to provide an improved method of;and apparatus for, cleaning textile fabric articles in which theagitation and circulation of the cleaning emulsion orother cleaningfluid through the articles to be cleaned are effected by the developmenttherein of ultrasonic waves.

In accordance with the invention, a machine for cleaning textile fabricarticles comprises an article container adapted to contain a cleaningfluid, an activator having a substantial surface area submerged in thecleaning fluid, and means for producing vibration of the activator at anultra-sonic frequency to activate the cleaning fluid.

Further in accordance with the invention, in a machine for cleaningtextile fabric articles, there is provided an activator comprising acup-like member of non-magnetic material having a high eddy currentimpedance, an elongated magnetostrictive element disposed in the member,and an ultra-sonic-frequency exciting winding surrounding the member. 1

Further in accordance with the invention, the

2 method of cleaning textile fabric articles comprises disposing thearticles in a cleaning fluid bath and developing ultra-sonlc-frequencywaves in said bath.

For a better understanding of the invention, together with other andfurther objects thereof, reference is had to the following description,taken in connection with, the accompanying drawings, while its scopewill be pointed out in the appended claims.

Referring now to the drawings, Fig. l is a longitudinal sectional viewof a cleaning and drying machine embodying the invention; Fig. 2 is atop view of the interior of the mechanism with the casing shown insection; Fig. 3 is a crosssectional detail of an activator embodied inthe apparatus of Fig. 1; Figs. 4 and 5 are schematic representations ofa modified form of machine embodying the invention; while Fig. 6 is across sectional detail of a modified form of activator for use in thecleaning and drying machine of the invention.

Referring now to Figs. 1, 2 and 3 of the drawings, there is representeda machine for cleaning textile fabric articles comprising an aperturedarticle container l0 adapted to contain a cleaning fluid, such as awashing emulsion, normally to a level Illa intermediate the depth of thecontainer. The container III is provided with a plurality of apertureslb and disposed around the periphery of the bottom thereof. A pluralityof activators II are individually disposed in the apertures llib andproject vertically upward therefrom.

Each of the activators II as shown more clearly in Fig. 3, comprises anelongated cup-like member Ila of nonmagnetic material and having a higheddy-current impedance, for example, of thermosetting plastic insulationmaterial such as Bakelite. Each of the members Ila has an annular flangelib adapted to be sealed to the periphery of the aperture lllb in whichthe activator is disposed. The activator II also includes an elongatedmagneto-strictive element disposed in the recess thereof and adapted toproject upwardly into the container ID. This magneto-strictive elementmay be of a hollow cylindrical shaft He and a disk-like head Ild securedthereto as by welding, brazing, or the like, and providing a substantialsurface area submerged in the cleaning fluid within the container Ill.The shaft I lc and head "d are constructed of magneto-strictive materialsuch as a high nickel or chrome alloy steel.

The activators I l are also provided with means for producing vibrationof the magneto-strictive element Hc, lid at an ultra-sonic frequency toactivate the cleaning fluid, for example, an ultrasonic winding liesurrounding the cup-like insulation member I la and provided with endterminals Hf connected to be excited from a suitable source It ofultra-sonic-frequency waves, for example, a conventional vacuum-tubeoscillator.

The cleanin machine of the invention also includes means for slowlyagitating or circulating the articles in the container to be cleaned,for example, a perforated basket l3 rotatably disposed in the containerID as by being mounted in a sleeve bearing I4 centrally disposed in thebottom of the container Ill. The basket I3 may be driven by a suitablemotor l5 through a pulley l5a attached to the motor IS, a pulley l3aattached to the shaft of the basket l3 and a belt l6.

The container l and the accessory devices described may be disposed on asupporting standard I1 and surrounded by an enclosed housing or casingl8 provided with a hinged cover I 8a to permit the clothes or articlesto be cleaned to 'be deposited in the container l0 and withdrawntherefrom. If desired, the container 10 may be provided with an openingI00 covered by a sliding door "id to prevent splashing of the cleaningfluid during cleaning.

The operation of the cleaning machine described above involves a novelmethod of cleaning textile fabric articles. After disposing the articlesto be cleaned in the cleaning fluid bath in the container l0, theultra-sonic frequency source is energized to developultra-sonic-frequency waves which are impressed upon the windings Ha ofthe several activators ll. When thus excited, longitudinalmagneto-strictive vibrations are developed in the shaft lie and itsattached disk H d which, in turn, develop ultrasonic-frequency waves inthe cleaning fluid bath lOa. These ultra-sonic-frequency waves, whendeveloped by activators such as those described,-

are in the form of a plurality of conical divergent beams directedvertically upward from each of the activators ll disposed at spacedpoints around the periphery of the bath. These beams produce standingcompression Waves within the cleaning fluid, the differential pressuresbetween the nodes and anti-nodes thereof producing a violentlow-amplitude circulation of the cleaning fluid through the articlesbeing cleaned. At the same time a moderate rotational agitation orcirculation of the articles in the bath is produced by the basket 13,thus insuring that all portions of the articles to be cleaned aresubjected to the action of the ultra-sonic-frequency beams. Aftercleaning as described, the articles may be withdrawn from the containerl0 and dried in any suitable well-known fashion.

In Fig. 4 there is represented schematically a modified arrangement ofthe activators in which the elongated activators 2| and their associatedoperating windings or devices Zla are disposed around the periphery ofthe container in with their axes in a direction having a substantialtangential component and pointing downward at an angle to thehorizontal, the activators pointing in the same rotational direction toinduce a circulatory motion of the cleaning fluid around the containerl0, as indicated by the arrows. The general principle of operation issimilar to that described above in connection with the apparatus of Fig.1.

The arrangement of Fig. is similar to that of Fig. 4 with the exceptionthat the activators II are disposed with their operating devices 2 laabove the normal fluid level in the container l0. so that no sealingdevices are required to prevent leakage of the cleaning fluid into theoperating mechanism or windings of the activators.

, In Fig. 6 is represented a modified form of activator which may beused in place of the magneto-strictive activator of Fig. 1. In this casethe activator 3| comprises a pot magnet 31a, similar to that used in aconventional dynamic loud speaker, and provided with an exciting winding3"; disposed in a spool 3| 0 of insulation material surrounding thecircular core 3ld of the magnet. The pot am and core 3ld provide anannular uniform air gap in which the magnetical field is also uniform.Disposed within the air gap is a vibratory element" comprising acylindrical shaft 3|! having a disk-like head lily of substantialsurface area and adapted to develop ultra-sonic-frequency waves withinthe cleaning fluid. Surrounding the shaft 3 I j is a winding 3le adaptedto be excited from an ultra-sonic-frequency source, such as the source Hof the Fig. 1.

The operation of the structure of Fig. 6 is entirely analogous to thatof a conventional diegrammatic loud speaker. excitation of the winding31b from a unidirectional source and excitation of the winding 31.2 froman ultra-sonicfrequency source producing ultra-sonic-frequency vibrationof the element 3!] am. If desired, the unidirectional-current windin 3lbmay be omitted and the pot 3la and core 3ld constructed of a permanentmagnet material of high retentivity. The activator of Fig. 6 may bemounted in the container 1 0 in a manner similar to that of any of Figs.1, 4 and 5.

The frequency of ultra-sonic-frequency source l2, or its equivalent.utilized to excite the activators of any of the several forms of theinvention illustrated must, of course, be .well above the audible rangein order to prevent severe discomfort to the operator. This indicatesalower limit of frequency of the order of 20 kilocycles per second. Onthe other hand it appears that the wave length of theultra-sonic-frequency waves developed in the cleaning fluid should notbe substantially shorter than the order of the thickness of the textilearticle being cleaned. Since the velocity of propagation of such wavesis the same as that of sound waves which, in water or in an aqueouscleaning solution, is of the order of 5,000 feet per second, an upperlimit of acceptable frequency is indicated as approximately 300kilocycles per second.

The development of ultra-sonic-frequency waves within the cleaning fluidresults in a number of features which cooperate to insure a thoroughcleansing action of the articles to be cleaned without substantialdeterioration of the fabric. The energy of the ultra-sonic waves isabsorbed in the cleaning fluid as heat. thereby aiding in maintaining aproper temperature of the washing mixture. It has also been found thatsuch supersonic-frequency waves in a liquid produce cavitation, that isthe formation of bubbles of air or vapor and their intense agitation,and this process accelerates the emulsiflcation of grease and dirtparticles by the soap or other detergent in the cleaning fluid. Suchultra sonic-frequency waves also, to a slight degree, break down themolecular structure of the water producing appreciable quantities ofhydrogen peroxide which aids in bleaching the clothes. Further, in casethe wash water is hard. containing substantial amounts of carbonates,the carbonates tend to be precipitated by the ultra-sonic-frequencywaves. thus softening the water. Such supersonic frequency-waves,particularly of the shorter wave lengths, tend to destroy bacteria orother simple organisms, thus having a certain sterilizin action.

While there have been described what are at present considered to be thepreferred embodiments of the invention, it will be apparent to thoseskilled in the art that various changes and modifications -may be madetherein without departing from the spirit or scope of the invention.

What is claimed as new is:

1. A machine for cleaning textile fabric articles comprising, acylindrical article container adapted to contain a cleaning fluid, aplurality of elongated activators arranged around the periphery of saidcontainer with their axes in a direction having a component tangent tothe periphery of said container, each of said activators having asubstantial surface area submerged in the cleaning fluid, and means forproducing vibration of said activators at an ultrasonic frequency toactivate the cleaning fluid.

2. A machine for cleaning textile fabric articles comprising, acylindrical article container adapted to contain a cleaning fluid, aplurality of elongated activators arranged around the periphery of saidcontainer with their axes in a direction having a component tangent tothe periphery of said container and at an angle to the horizontal, saidactivators all pointing in the same rotational direction, each of saidagitators having a substantial surface area submerged in the cleaningfluid, and means for producing vibration of said activators at anultra-sonic frequency to activate the cleaning fluid.

3. The method of cleaning textile fabric articles which comprises,disposing the articles in a cleaning fluid bath, and developing aplurality of beams of ultra-sonic-frequency waves at spaced points insaid bath and in directions having components in the same rotationaldirection.

4. In a machine for cleaning textile fabric articles including a maincontainer adapted to contain a cleaning fluid, an activator comprising acup-like member of non-magnetic material having a high eddy currentimpedance and adapted to be disposed in said container, sealing meansfor preventing cleaning fluid from entering said cup-like member, anelongated magnetostrictive element disposed in said member and having asubstantial surface area adapted to project into cleaning fluid whichmight be disposed in said container, and an ultra-sonic-frequencyexciting winding surrounding said member.

HAL F. FRUTH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 369,299 Rubenstein Aug. 30, 1887733,481 Holman July 14, 1903 1,318,740 Fessenden Oct. 14, 1919 1,580,476Fassio Apr. 13, 1926 1,586,877 Buckley June 1, 1926 1,966,446 Hayes July17, 1934 2,076,280 Schroeder Apr. 6, 1937 2,163,649 Weaver June 27, 19392,168,068 Loweke Aug. 1, 1939 2,203,479 Witwer June 4, 1940 FOREIGNPATENTS Number Country Date 691,392 France July 8, 1930 504,625 GermanyAug. 6, 1930 506,538 Germany Sept. 5, 1930 548,960 Great Britain Oct.30, 1942 1,592 Australia July 28, 1931

